python3 fix

Author: gsmolk

testgres/testgres.py

@@ -457,7 +457,7 @@ def get_control_data(self):
             lines = subprocess.check_output(
                 [pg_controldata] + ["-D", self.data_dir],
                 stderr=subprocess.STDOUT
-            ).splitlines()
+            ).decode("utf-8").splitlines()
         except subprocess.CalledProcessError as e:
             raise PgcontroldataException(e.output, e.cmd)